5. I looked it up

out of curiosity.

You’re supposed to eat the fruit, peel and all, because there really is nothing BUT the peel.

There is more information here:

Buddha’s Hand Citrons
Called a Buddha’s Hand Citron, this odd looking fruit is actually one of the oldest members of the citrus family. Although it smells strongly of lemon, it has no juicy pulp hidden beneath its rind. Instead, the Buddha’s Hand is grown commercially for its powerful zest. The aromatic rind is used to flavor lemon liqueurs and specialty vodkas, and provides aroma to lemon-scented cosmetics. Chinese and Japanese households hang it in their homes as a natural air freshener, and it even has a place in some religious ceremonies.